1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and the like, particularly, it relates to an image forming apparatus including a simultaneous multicolor copying mode.
2. Description of Related Art
In an image forming apparatus such as an electrophotographic copying machine, there is an apparatus in which a plurality of developing units are disposed and developing colors are switched during one scanning operation to obtain a multicolor copy. When copying is performed in the simultaneous multicolor copy mode, developing colors and switching positions are designated in advance. In the simultaneous multicolor copy mode, respective developing units are operated according to the designation so as to obtain the multicolor copy by one scanning (refer to the U.S. patent application Ser. No. 148,423).
While, some copying machines are provided with an interrupt copying function. When interrupt copying is designated, the present copying mode is stored and shunted and the other copying mode can be used. Thereafter, the copying mode shunted is restored and copying in the original copying mode can be continued.
As a designating method for the developing color switching position in the simultaneous multicolor copy, for example, by a position designating lever provided slidably near a document glass platen, the lever position is designated in the sliding direction and detected to switch the developing colors.
Now, in a copying machine in which both the simultaneous multicolor copying and interrupt copying are possible, there is the possibility that simultaneous multicolor copying is interrupted. In this case, the developing color switching position may be changed at interrupt copying. For example, such as a case wherein the lever position has been moved to a desired position without releasing designation of the simultaneous multicolor copy at the interrupt copying. In this case, when returning to the simultaneous multicolor copy mode from the interrupt copying, it is difficult to return to the original lever position, so that there is the possibility of causing miscopying.
In order to solve this problem, though the switching position can be stored and returned automatically to the original position at completion of interruption, it requires a large-scaled apparatus.